.\" RCSid "$Id: ra_rgbe.1,v 1.2 2003/12/09 15:59:06 greg Exp $"
.TH RA_RGBE 1 1/23/98 RADIANCE
.SH NAME
ra_rgbe - convert between different RADIANCE picture types
.SH SYNOPSIS
.B ra_rgbe
[
.B \-r
][
.B "\-e +/-stops"
][
.B \-f
][
.B "\-n frameno"
]
[
.B input
[
.B outspec
]
]
.SH DESCRIPTION
.I Ra_rgbe
converts between RADIANCE run-length encoded and flat formats, and
separates concatanated animation frames produced by
.I rpict(1).
The
.I \-e
option specifies an exposure compensation in f-stops (powers of two).
Only integer stops are allowed, for efficiency.
By default,
.I ra_rgbe
produces a flat RADIANCE picture file from any type of RADIANCE
input picture.
The
.I \-r
option causes
.I ra_rgbe
to produce a run-length encoded file instead.
.PP
If the input file consists of multiple animation frames as produced by
.I rpict
with the
.I \-S
option,
.I ra_rgbe
will read each frame and write it to the output file created by calling
.I printf(3)
with the output specification and frame number as arguments.
If the output specification begins with an exclamation mark ('!'),
then this interpreted as a command spec., which is also run through
.I printf
with the frame number to get the final command.
This command must accept a Radiance picture on its standard input,
and may write results either to a file or to the standard output.
The
.I \-n
option may be used to select a specific frame for output, and
other frames in the input will be skipped.
Normally, all frames will be read and written.
.PP
.I Ra_rgbe
will report an error and exit if the target output file already exists,
unless the
.I \-f
option is given.
If the output file is missing, the standard output is used.
If the input file is missing or set to '-', the standard input is used.
.SH NOTES
The file format for RADIANCE pictures was changed between release
1.4 and release 2.0.
The older format can still be read by all the programs, but only
the newer format is produced.
This newer format cannot be read by RADIANCE software prior to
release 2.0.
.PP
.I Ra_rgbe
provides some downward compatibility by producing files that can
be read by older RADIANCE software.
The resultant files are also easier to manipulate with programs
designed to read raw raster data.
.PP
The other use for
.I ra_rgbe
is as a quicker way to adjust the exposure of a RADIANCE picture than
.I pfilt(1),
since
.I ra_rgbe
only allows integer f-stop changes.
In this mode,
.I ra_rgbe
should be used with the
.I \-r
option.
.SH AUTHOR
Greg Ward
.SH ACKNOWLEDGEMENT
Work on this program was initiated and sponsored by the LESO
group at EPFL in Switzerland.
.SH "SEE ALSO"
pfilt(1), printf(1), ra_xyze(1), rpict(1)
